(1) Field of the Invention
This invention relates to document feeding and more particularly to the creation of a shingled stack of original documents and the feeding of single documents therefrom.
(2) Description of Prior Art
In order to free the user from giving constant attention to the copier, the increased automation of functions associated with copying is becoming more desirable. An example of such a function is the supply of original documents to the imaging station of the copier.
Automatic feeders are well known in the copier field, but primarily for the automatic feeding of copy sheets to the transfer station of the copier. Such feeders consistently feed the same size and same type of paper and thus can be highly specialized and adapted to the particular paper employed, and need not consider whether print would be marred.
The automatic feeding of original documents, however, should accommodate a wide range of papers varying, for example, in weight and texture. The feeder should conveniently separate each sheet from a stack and feed it singly without marking the sheet or marring the print. Prior feeding systems do not attain this goal and are limited in effectiveness to a specific narrow range of originals, or to a geometry (e.g., vertical sheets) that is difficult for a casual operator to use or understand.
The most convenient arrangement from the standpoint of the user is a bottom feed where the operator simply places a stack of originals in numerical order face down in a tray.
Bottom feeding, however, poses difficult problems for prior feeding arrangements. Friction pickers comprising a friction roll at the bottom of the tray often tend to pick many sheets at once, and beating or shingler wheels at the bottom of the tray combined with a nip pair of feed rollers tend to drag out sheets resting on top of the first sheet.
Examples of these arrangements included Hoyer, U.S. Pat. No. 3,861,671, "Liftable Bail Bar for Allowing Return of Multi-Ply Separated Sheets to Stack," showing vertical sheets fed by a friction roll to a feed roll and reversing roll; Hauser, U.S. Pat. No. 3,937,455, "Automatic Stack Feed," showing vertical sheet separated by a beating means to a feed roll and reversing roll; Sahley, U.S. Pat. No. Re. 27,976, "Document Feeder," showing a bottom friction feed for feeding sheets through a feed slot to a roller conveyor; Hunt, IBM Technical Disclosure Bulletin, Vol. 19, No. 10, March 1977, pp. 3628-3629, "Envelope Shingling Apparatus," shows a shingler wheel bottom feed of envelopes through a clump feed gate; Avritt, IBM Technical Disclosure Bulletin, Vol. 20, No. 2, July 1977, p. 496, "Bottom Sheet Paper Feed," shows a combination shingler wheel and belt feed; and Hunt et al, IBM Technical Disclosure Bulletin, Vol. 20, No. 2, July 1977, P. 497, "Sheet Shingler," shows a chain shingler.